US2521844A

US2521844A - Antenna

Info

Publication number: US2521844A
Application number: US629157A
Authority: US
Inventors: Walter O Gordy
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-11-16
Filing date: 1945-11-16
Publication date: 1950-09-12
Anticipated expiration: 1967-09-12

Description

Sept. 12, 1950 w. o. GORDY 2,521,844

ANTENNA Filed Nov. 16, 1945 IN V EN TOR. WALTER O. GOR DY BY ATTORNEY Patented Sept. 12, 1950 UNITED STATES O FFICE- v. Q 6 4 .1 I i I r f t I I 7 Walter o. Gordy,Cambridge,Masss assignor, by?1 mesne assignments, to the Unitedn ta e 9 America as represented by the Secretary of War 1 Application November 16, Serial No. 629,151

, 4 Claims. (01. 250%3353) This invention relates to antennas and more The scanning actionmay beproduced entirely by electrical .means, ormay be accomplished by mechanical motion, for, ex

ample by movement of the antenna itself'orof an element thereof.

A scanner devised by John S. Foster, application Serial No. 657,156, filed March 26, 1946, to which the instant invention is related, employs what may be termed a conical shell Waveguide and. is hereinafter brieflyconsidered inorderto betterdescribe the present ,i lVention.

In the Foster scanner, only a single-beam of electromagnetic. radiation is emitted at any one time. The presentinvention is an improvement thereon whereby two scanning beams of electro;

magnetic energy may be simultaneously directed from the one antenna system. v

Among the objects of this invention are; ,to provide a single conical shellwaveguide antenna which will scan two defined sectors of space separately and simultaneously; an P i a conical shell waveguide. scanner which is compact in structure and light in weight, considering'the large sectors of space swept by the scanner.

features of this invention will become apparent from the description contained herein taken with the drawings accompanying this specification; in which:

Fig. 1 is a cross-sectional view of a Foster coni- -cal shell waveguide scanner; t v H c Fig. 2 is a cross-sectional view of a preferred embodiment of the present invention;

Fig. 3 illustrates in perspective the external appearance'of the waveguide scannerof the'invention; and

Fig, 4 illustrates the geometry applicable to a radar system employing the pres'entinvention. Referring. now to Fig. 1, 'there is illustrated a cross-sectional view of a conical shell waveguide Further objects and, ,ethr advantages and defined sectorof space linearly. with time. at a 19 rapid rate.

region where a conventional. waveguide transmission line 'connectsto an inner member of the scanner. The conical shell waveguide is formed by outer and inner members H andl2 providing substantially parallel outer and inner conical surfaces l3 and M, respectively. The sepa-' 'rationbetween surfaces l3 and His preferably less than .one-half wavelength 'atthe contem plated operating frequencies. Inthe described embodiment of this Foster scanner, member 1 I is stationary, and member. [2 is .rotatable about longitudinal aperture; is provided. inthe inner or rotor member I2, .as shown, extending 'substantially alonglinearelements of conicalsurfac'eM. A similar longitudinal aperture I1 is provided in outer member I l, extending substantially along linear elements of conical surface l3. Energy may be introduced to the system through a waveguide I8 extending coaxially into the rotor 'memb'er: of the structure and communicating with a branching waveguide l9. .Energy may be-fed into or extracted from the rotor memher" by use of a rotating joint, not shown,:pro-.

'vided' at one end of waveguide l8. .Waveguide i9 is secured to the rotonmember l2, and at directed toward a third reflecting surface shaped in the form of a-parabolic cylinder: of comparatively small height.-' Wave energy directed into suchastructur'e-toward the reflecting surface, from theneighborhood of thefocal line defined by the'par' 'abolic surface, wil'lbe'. reflected with a wavefront normal to the axialplane of theparab o lic'surface. Pillbo'x?! is-such a' structure, ex- "cept that hereits surfaces "-arecurved or de formed, in order'toifit within rotor. land in order to provide an emanating wave front at longi-' tudinal pertu e-15' which corresponds with the open end'terrnination of pillbox' l2f Theemanatin wave front 'at' aperture I Em'ay be substan :tiallyparallel to the line; elements" of conical s'ur face [4 at aperture l 6. The feed j apertdiefzo tr waveguide I9 is located in theneighborhoodof the focal'point of the parabolic reflecting surface :2 of'pillboxlzg' I I A series'of'teethln, adapted to reflect or direct clockwise direction and is refiectedintoiaperture 32 by reflecting teeth a; likewise; electromag -netic energy fed from branching-waveguide 44 to pillb'ox 42 is-directed by reflecting teeth-Mbinto conical shell waveguide 29, traveling clockwise "therethrough until directed out'of aperture' 32 by reflecting teeth 35b. As inner member-3i of the structure is rotated, electromagnetic'energy emanates from aperture 32 in two separate beams which recurrently scan, in. the sameplane, sectors which have substantially equal anglesin the embodiment illustrated The. salient members 35 and 40- are arranged to slip past each other so that continuous rotation may be achieved." If

:desired, two separateaperturesmay. be utilized forthe transmission :of energy from waveguide 2.9,

instead of using an aperture 'dividedzby a partition, as shown. Similarly, two angular-1y. separated apertures maybe .utilizedffor thetransmls- :sion of energy into conical waveguide 29,.rather .than-using adjacent apertures 31'.and;38 as in the embodiment herein disclosed. It will be understood that arranging the apertures and reflectors as shown, however, permits use of a single re- .flectgr illuminated by .theenergy from-both. apertures. A

Referring now to Fig. 3, there is illustrated in perspectii 'e the external appearance of the conical shell waveguide scanneriof Fig. 2, likez'parts having like reference numerals appliedzthereto. The outer surface of member 30 may be conical in shape to conform to its inner surface 33. An

auxiliary reflector may be used to increase the effective gain of the antenna system. Thus, a parabolic cylinder reflector 50 may be utilized, held in fixed relation to the scanner structure proper by members 5| as shown. Reflecting surface 52 of the parabolic cylinder reflector 5| may have its focal axis substantially along the line of aperture 32. Such a portion of the parabolic cylinder surface may be used that the reflected electromagnetic waves travel outwardly therefrom in a plane spaced from and parallel to the axial plane of the parabolic cylinder, so that the conical waveguide scanner may be in a non-interfering position relative to the reflected beams.

The conical waveguide scanner of Fig. 2 may be constructed so that the two radiated beams may scan separate sectors, as angle A and angle B of Fig. 3. This result may be accomplished in the embodiment herein disclosed by suitably orienting the structure of pillboxes 4| and 42 within the rotor member 3|. If linear arrays, lens systems, or other means are utilized for providing electromagnetic energy having plane Wave fronts at longitudinal apertures in the inner surface of the conical shell waveguide, a similar effect may be accomplished by proper phasing or alteration of the elements thereof.

It will be assumed, as before, that rotor member 32 turns in a clockwise direction as seen in Fig. 2 of the drawing.

Referring again to Fig. 3, lines A-l and A--2 respectively indicate, for the two positions of the rotor wherein salient members 40 are positioned immediately clockwise and counterclockwise, respectively, relative to salient members 35, the directions which may be taken by energy which has traveled in a counterclockwise direction through waveguide 30. Similarly, lines 3-! and B-2 respectively indicate the directions which may be taken by energy which has traveled in a clockwise direction through wave guide 29.

Thus the cycle of scan for sectors A and B in the disclosed embodiment starts with the beams ai ing-cycle. 11 Theutility'of such a'two-sector scanning struc ture Lmay be understood by reference to 4 which-illustrates the geometry of a radio echo detection ,and ranging: system using :theconical in/positions A-=-| and B-l'," the beams sweeping toward the positions A2- andB-f-I during the scanning cycl'e,-':andlstarting 'again'frdmiposltions .A l 'and-B l.-Jat the beginning of thenext'sc shell: waveguideiscanner herein disclosednA vessel .60 is diagrammed navigating surface waters. The structureillustrated in:Fig.=3 may be mount -:ed on vessel 60.;with aperture:32. and ir'eflector: 50 .inpaigenerallyverticalposition.) In Figs! are .dia

gramm'ed;thecsectors having angles A..and IB;-::-'It

will lbehobserved therefrom thattheibeamaaof energy sweeping sector B may start alongl-ar line r B-l, which is substantially.-horizontal, andtsweep through-a sectonB. c. Similarly; theeother-beam maystart along av substantially yerticallineAe-wl and sweep througha sector Ahavinga: like angle."

At the completion of a scanning -cycle; :.the t'wo beamsgmay .be. substantially-.7 codirectional; Izas shown. 'Ihe antenna structure may. beirevolved in azimuthto obtainooverage of an entireseg-j mentof space about; vessel 60.. {Ifhe systemdee scribed may .thus simultaneously vsatisfy ,1in; gen-r eral; the {requir men s f both .adoneganse and -renegsyste rorhthebeam. sweepinathe ow r ev n sector B cani arryiereaterzpower.

or gre ater antenna gaimthan tha swe ping the f (In practical radar systems, far-distant targets, requiring greater higher elevation sector A.

may thus be accomplished by use of the present invention. A further advantage resides in the complete coverage of the total angle A plus B. which is otherwise difllcult to secure.

4 In a radar system utilizing the antenna structure here described, echoes returned from distant Objects may be located in elevation by their timed relationship to the period of the scan. The scanning is linear with the rotation of the rotor, so that with the rotor turned at a constant speed, the angular displacements of the beams are linear with time. Consequently, such timed relationship may be established through the use of linear sweep circuits, as well as other means, synchronized with the rotor rotation. Moreover,

signals returning from both beams may be simultaneously displayed on a single oscilloscope designed to display the signal range as plotted against elevation angle.

Although the description and discussion of the conical waveguide scanner has here been considered from the viewpoint only of energy radi-" ated from the scanner it will be apparent to those;-

skilled-inthe radio art that the scanner is a linear device, which will transmit energyequally well in a reverse direction with like directive In other words, as already assumed in connection with the discussion of Fig. 4, where qualities.

signals are both sent and received by the radar system antenna, the conical shell wave guide scanner of the invention may be used equally.

well and with like directive qualities for either transmission or reception of electromagnetic energy.

The scanner or this invention may also be def l ke 'SBImG SGTGtOES, -.so= that the-,scanning= angle is cnvened byeboth; beams-:crossing eachwother. This designirmightbe useful in 'locating bymadar a hidden source of shell fire by observing the echoes retmmedaat angles which indicate the path'ionorbit=offithe projectile. The present inmentiomthusqaiffordssa convenient :means f or ;providingjzaad'ouble beam itoisatisfy the requirements ofrmany'electromagnetic radiation systems.

Nariations in the" retructure herein :described as canrxembodiment of. :the invention will be apparent tb those'skiHedz init'he radio and waveguide arts. Therefore it'ais .not desired to restrict the inventicmito the precise embodiment-herein dis- Mosedmorito :the particular usage herein .de-

scfiibei,

- 21].. #1A.'i waveguide structure iofiel'ectromagnetic enegyy iinehidin'g :imier and 'outer n'iembersdefining 22a substantially 'conical shell waveguide, 5am in'zier'=member providing the inner surface-of isaid m'oiiieal ishell: waveguide and having awe longitudinal 'inrier apeitures therein, said outer member :providing the outer coaxial surface of r saixl cconical' si'iell waveguide and having two lefig'itudinal outer apertures therein-inner surface eneizgy-idirectirigi members arranged between saiiitliiin'er "apertures and extending into said conical shellwaveguide from said inner member, za'iid out'er surfaee energydirecting members ;-8 arranged :be.tween.'said mu ter zap'erturesgand 1e15- itendingwinto gsaidsteonical .shel-l wave uide 12mm .saidioutermembemwherebmenerg zniayibetranslf-EBIGd between eaiehfiof said, inner'-1suri ace (ape;- sturesand areal-"responding;;outer-;su1;fi'aee aperture icireumferentially through said conical-g -shell Waveguide q :TheWaveguide=-structurerof c1aim:.-1=wherein e-saidfinnernnember': an d" itsenergy-directirig; members .arearotxatablewajbout theeconmiomaxis oiisaid (coaxial :surfia'ces, :and wherein :said (eIiH/ yfidi' :rectingrmembers are'lin the zior'maof teethwa'dapted [to 'slipipast each rather lupon-zrotation oft-said inner'member.

iThewaveguideustructure *oi"claim s1 .wherein saidiinnerr member'. andiits energyeiiireetingrinemberszrare rotatable about the commomaxistofnsaid coaxialisutfacesw e (r55:

Thefwaveguidmstructurecof claim d iurther including means withinv-said drmier 'rstmmturez ibr transferringcenerg'y-:thmugh said'innerapertures.

'WMEBER-TOJGQRDY.

v 1 EEEERENeEsemEn The wwwmg references la re' of record m the file oi this patent: